The present invention relates to systems for the transport and recirculation of charged particle beams and more particularly to such a system that is passive, completely achromatic and nearly isochronous.
The recirculation of energized particles in, for example, a particle accelerator, free electron laser or the like device is a well recognized method and much effort has been devoted to the design and implementation of a variety of systems to reduce the technical requirements of such systems while providing a recirculated particle beam that is of relatively uniform cross-sectional profile, i.e. well defined, timed to meet the requirements of the acceleration field, and linearly consistent. The objective in such systems is, of course, to be able to produce a focused and compact stream of particles and to reintroduce that stream of particles into the accelerator field at the appropriate time so as to achieve maximum energization thereof, or, alternatively, to make the particles coincident with a decaying portion of the oscillating field so as to impart the particle energy to the accelerator field. Additionally, the temporal behavior of the recirculated particle beam should be should be consistent, i.e. bunches of particles should remain linearly arranged. The production of such a recirculated particle beam, of necessity because of the design of accelerators and the like, requires that the beam be bent or turned from one xe2x80x9cexitxe2x80x9d position as it exits the accelerator and reinserted into a xe2x80x9cstartxe2x80x9d or introduction point up stream of the exit point Such manipulation of the beam generally requires bending the beam through two 180xc2x0 turns as will be described further below in connection with FIG. 1.
Currently used systems may utilize very intense and uniform magnetic fields to achieve this particle beam manipulation and often affect the timing, profile and bunch, i.e. linear, arrangement within the recirculated particle beam.
It is therefore an object of the present invention to provide a simplified solution the problem of turning the recirculated particle beam.
It is another object of the present invention to provide a particle beam turning system that requires less intense and/or uniform magnetic fields.
It is yet a further object of the present invention to provide a particle beam bending system that is nearly isochronous, i.e. maintains the temporal characteristics of the recirculated beam, and is otherwise less invasive on the properties of the transported beam of particles.
It is yet another object of the present invention to provide a particle beam bending system that supplies a recirculated particle beam that well ordered in terms of bunch location therein, i.e. the path length of the particle trajectories should vary only linearly with particle momentum.
According to the present invention, there is provided a particle beam bending system having a geometry that applies active bending only beyond the chord of the orbit for any momentum component. As a consequence, all momentum components emerge dispersed in position only; all trajectories are parallel by construction. Combining a pair of such bends with reflective symmetry produces a bend cell that is, by construction, achromatic to all orders. By the particular choice of 45xc2x0 individual bends, a pair of such achromats can be used as the basis of a 180xc2x0 recirculation arc. Other rational fractions of a full 180xc2x0 bend serve equally well (e.g., 2 bends/cellxc3x9790xc2x0/bendxc3x971 cell/arc; 2 bends/cellxc3x9730xc2x0/bendxc3x973 cells/arc, etc), as do combinations of multiple bending numerologies (e.g., 2 bends/cellxc3x9722.5xc2x0/bendxc3x972 cells+2 bends/cellxc3x9745xc2x0/bendxc3x971 cell).